Hydroxysteroid dehydrogenases (HSDs) regulate the occupancy and activation of steroid hormone receptors by converting steroid hormones into their inactive metabolites. For a recent review, see Nobel et al., Eur. J. Biochem. 2001, 268: 4113-4125.
There exist numerous classes of HSDs. The 11-beta-hydroxysteroid dehydrogenases (11β-HSDs) catalyze the interconversion of active glucocorticoids (such as cortisol and corticosterone), and their inert forms (such as cortisone and 11-dehydrocorticosterone). The isoform 11-beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is widely expressed in liver, adipose tissue, brain, lung and other glucocorticoid tissue, while the isoform 2 (11β-HSD2) expression is limited to tissues that express the mineralocorticoid receptor, such as kidney, gut and placenta. Then the inhibition of 11β-HSD2 is associated with serious side effects, such as hypertension.
Excess cortisol is associated with numerous disorders, including diabetes, obesity, dyslipidemia, insulin resistance and hypertension. The administration of 11β-HSD1 inhibitors decreases the level of cortisol and other 11β-hydroxysteroids in target tissues, thereby reducing the effects of excessive amounts of cortisol and other 11β-hydroxysteroids. Thus, 11β-HSD1 is a potential target for therapy associated with numerous disorders that may be ameliorated by reduction of glucocorticoid action. Therefore, the inhibition of 11β-HSD1 can be used to prevent, treat or control diseases mediated by abnormally high levels of cortisol and other 11β-hydroxysteroids, such as diabetes, obesity, hypertension or dyslipidemia. Inhibition of 11β-HSD1 activity in the brain such as to lower cortisol levels may also be useful to treat or reduce anxiety, depression, cognitive impairment or age-related cognitive dysfunction (Seckl, et al., Endocrinology, 2001, 142: 1371-1376).
Cortisol is an important and well recognized anti-inflammatory hormone, which also acts as an antagonist to the action of insulin in the liver, such that insulin sensitivity is reduced, resulting in increased gluconeogenesis and elevated levels of glucose in the liver. Patients who already have impaired glucose tolerance have a greater probability of developing type 2 diabetes in the presence of abnormally high levels of cortisol (Long et al., J. Exp. Med. 1936, 63: 465-490; Houssay, Endocrinology 1942, 30: 884-892). In addition, it has been well substantiated that 110-HSD1 plays an important role in the regulation of local glucocorticoid effect and of glucose production in the liver (Jamieson et al., J. Endocrinol. 2000, 165: 685-692). In Walker, et al., J. Clin. Endocrinol. Metab. 1995, 80: 3155-3159, it was reported that the administration of the non-specific 11β-HSD1 inhibitor carbenoxolone resulted in improved hepatic insulin sensitivity in humans.
Furthermore, the hypothesized mechanism of action of 11β-HSD1 in the treatment of diabetes has been supported by various experiments conducted in mice and rats. These studies showed that the mRNA levels and activities of two key enzymes in hepatic glucose production, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6 Pase) were reduced upon administration of 11β-HSD1 inhibitors. In addition, blood glucose levels and hepatic glucose production were shown to be reduced in 11β-HSD1 knockout mice. Additional data gathered using this murine knockout model also confirm that inhibition of 11β-HSD1 will not cause hypoglycemia, since the basal levels of PEPCK and G6Pase are regulated independently of glucocorticoids (Kotelevtsev et al, Proc. Natl. Acad. Sci. USA 1997, 94: 14924-14929).
Therefore, the administration of a therapeutically effective amount of an 11β-HSD1 inhibitor is effective in treating, controlling and ameliorating the symptoms of diabetes, especially non-insulin dependent diabetes (NIDDM, type 2 diabetes mellitus) and administration of a therapeutically effective amount of an 11β-HSD1 inhibitor on a regular basis delays or prevents the onset of diabetes, particularly in humans.
The effect of elevated levels of cortisol is also observed in patients who have Cushing's Syndrome, which is a metabolic disease characterized by high levels of cortisol in the blood stream. Patients with Cushing's Syndrome often develop NIDDM.
Excessive levels of cortisol have been associated with obesity, perhaps due to increased hepatic gluconeogenesis. Abdominal obesity is closely associated with glucose intolerance, diabetes, hyperinsulinemia, hypertriglyceridemia and other factors of Metabolic Syndrome, such as high blood pressure, elevated VLDL and reduced HDL (Montague et al., Diabetes, 2000, 49: 883-888). It has also been reported that inhibition of the 11β-HSD1 in pre-adipocytes (stromal cells) resulted in a decreased rate of differentiation into adipocytes. This is predicted to result in diminished expansion (possibly reduction) of the omental fat depot, which may lead to reduced central obesity (Bujalska et al., Lancet 1997, 349: 1210-1213).
Thus, the administration of an effective amount of an 11β-HSD1 inhibitor is useful in the treatment or control of obesity. Long-term treatment with an 11β-HSD1 inhibitor is also useful in delaying or preventing the onset of obesity, especially if the patient uses an 11β-HSD1 inhibitor in combination with controlled diet end exercise.
By reducing insulin resistance and maintaining serum glucose at normal concentrations, compounds of the present invention also have utility in the treatment and prevention of conditions that accompany type 2 diabetes and insulin resistance, including the Metabolic Syndrome, obesity, reactive hypoglycemia and diabetic dyslipidemia.
Inhibition of 11β-HSD1 in mature adipocytes is expected to attenuate secretion of the plasminogen activator inhibitor 1 (PAI-1), which is an independent cardiovascular risk factor, as reported in Halleux et at, J; Clin. Endocrinol. Metab. 1999, 84: 4097-4105. In addition, a correlation has been shown to exist between glucocorticoid activity and certain cardiovascular risk factors. This suggests that a reduction of the glucocorticoid effects would be beneficial in the treatment or prevention of certain cardiovascular diseases (Walker et at, Hypertension 1998, 31: 891-895; and Fraser et at, Hypertension 1999, 33: 1364 1368).
Since hypertension and dyslipidemia contribute to the development of atherosclerosis and inhibition of 11β-HSD1 activity and a reduction in the amount of cortisol are beneficial in treating or controlling hypertension, administration of a therapeutically effective amount of an 11β-HSD1 inhibitor of the present invention may also be especially beneficial in treating, controlling or delaying the onset of or preventing atherosclerosis.
11β-HSD1 has also been implicated in the process of appetite control and therefore is believed to play an additional role in weight-related disorders. It is known that adrenalectomy attenuates the effect of fasting to increase both food intake and hypothalamic neuropeptide Y expression. This suggests that glucocorticoids play a role in promoting food intake and that inhibition of 11β-HSD1 in the brain may increase satiety, thus resulting in a decreased food intake (Woods et al., Science 1998, 280: 1378-1383).
Another possible therapeutic effect associated with modulation of 11β-HSD1 is that which is related to various pancreatic aliments. It is reported that inhibition of 11β-HSD1 in murine pancreatic β-cells increases glucose stimulated insulin secretion (Davani et al., J. Biol. Chem. 2000, 275: 34841-34844). This follows from the preceding discovery that glucocorticoids were previously found to be responsible for reduced pancreatic insulin release in vivo (Billaudel et al., Horm. Metab. Res. 1979, 11: 555-560). Thus, it is suggested that inhibition of 11β-HSD1 would yield other beneficial effects in the treatment of diabetes other than the predicted effects on the liver and of fat reduction.
Excessive levels of cortisol in the brain may also result in neuronal loss or dysfunction through the potentiation of neurotoxins. Administration of an effective amount of an 11β-HSD1 inhibitor results in the reduction, amelioration, control or prevention of cognitive impairment associated with aging and of neuronal dysfunction. Cognitive impairment has been associated with aging, and excess levels of cortisol in the brain (see J. R. Seckl and B. R. Walker, Endocrinology, 2001, 142: 1371 1376, and references cited therein). 11β-HSD1 also regulates glucocorticoid activity in the brain and thus contributes to neurotoxicity (Rajan et al., Neuroscience 1996, 16: 65-70; Seckl et at, Necroendocrinol. 2000, 18: 49-99). Stress and/or glucocorticoids are known to influence cognitive function (de Quervain et al., Nature 1998, 394: 787-790), and unpublished results indicate significant memory improvement in rats treated with a non-specific 11β-HSD1 inhibitor. These reports, in addition to the known effects of glucocorticoids in the brain, suggest that inhibiting 11β-HSD1 in the brain may have a positive therapeutic effect against anxiety, depression and related conditions (Tronche et al., Nature Genetics 1999, 23: 99-103). 11β-HSD1 reactivates 11-dehydrocorticosterone to corticosterone in hippocampal cells and can potentiate kinase neurotoxicity, resulting in age-related learning impairments. Therefore, selective inhibitors of 11β-HSD1 are believed to protect against hippocampal function decline with age (Yau et at, Proc Natl. Acad. Sci. USA 2001, 98: 4716-4721). Thus, it has been hypothesized that inhibition of 11β-HSD1 in the human brain would protect against deleterious glucocorticoid-mediated effects on neuronal function, such as cognitive impairment, depression, and increased appetite.
Furthermore, 11β-HSD1 is believed to play a role in immunomodulation based on the general perception that glucocorticoids suppress the immune system. There is known to be a dynamic interaction between the immune system and the HPA (hypothalamic-pituitary-adrenal) axis (Rook, Baillier's Clin. Endocrinol. Metab. 2000, 13: 576-581), and glucocorticoids help balance between cell-mediated responses and humoral responses. Increased glucocorticoid activity, which may be induced by stress, is associated with a humoral response and as such, the inhibition of 11β-HSD1 may result in shifting the response towards a cell-based reaction. In certain disease states, such as tuberculosis, leprosy and psoriasis, and even under conditions of excessive stress, high glucocorticoid activity shifts the immune response to a humoral response, when in fact a cell based response may be more beneficial to the patient. Inhibition of 11β-HSD1 activity and the attendant reduction in glucocorticoid levels on the other hand shifts the immune response toward a cell based response (D. Mason, Immunology Today, 1991, 12: 57-60, and G. A. Vt. Rook, Baillier's Clin. Endocrinol. Metab., 1999, 13: 576-581). It follows then, that an alternative utility of 11β-HSD1 inhibition would be to bolster a temporal immune response in association with immunization to ensure that a cell based response would be obtained.
Recent reports suggest that the levels of glucocorticoid target receptors and of HSDs are connected with the susceptibility to glaucoma (J. Stokes et al., Invest. Ophthalmol. 2000, 41: 1629-1638). Further, a connection between inhibition of 11β-HSD1 and a lowering of the intraocular pressure was recently reported (Walker et al., poster P3-698 at the Endocrine society meeting Jun. 12-15, 1999, San Diego). It was shown that administration of the nonspecific 11β-HSD1 inhibitor carbenoxolone resulted in the reduction of the intraocular pressure by 20% in normal patients. In the eye, 11β-HSD1 is expressed exclusively in the basal cells of the corneal epithelium, the non-pigmented epithelium of the cornea (the site of aqueous production), ciliary muscle, and the sphincter and dilator muscles of the iris. In contrast, the distant isoenzyme 11-hydroxysteroid dehydrogenase type 2 (“11β-HSD2”) is highly expressed in the non-pigmented ciliary epithelium and corneal endothelium. No HSDs have been found at the trabecular meshwork, which is the site of drainage. Therefore, 11β-HSD1 is suggested to have a role in aqueous production and inhibition of 11β-HSD1 activity is useful in reducing intraocular pressure in the treatment of glaucoma.
Glucocorticoids also play an essential role in skeletal development and function but are detrimental to such development and function when present in excess. Glucocorticoid-induced bone loss is partially derived from suppression of osteoblast proliferation and collagen synthesis, as reported in C. H. Kim et al., J. Endocrinol. 1999, 162: 371 379. It has been reported that the detrimental effects of glucocorticoids on bone nodule formation can be lessened by administration of carbenoxolone, which is a non-specific 11β-HSD1 inhibitor (C. G. Bellows et al., Bone 1998, 23: 119-125). Additional reports suggest that 11β-HSD1 maybe responsible for providing increased levels of active glucocorticoid in osteoclasts, and thus in augmenting bone resorption (M. S. Cooper et al., Bone 2000, 27: 375-381). This data suggests that inhibition of 11β-HSD1 may have beneficial effects against osteoporosis via one or more mechanisms which may act in parallel.
11β-HSD1 inhibitors are known e.g. from the WO0410629, WO03065983, WO04089896, WO04089380, WO04065351, WO04033427 or WO04041264. However, 2-adamantylurea derivatives are not disclosed as active 11β-HSD1 inhibitors.
Adamantylurea derivatives are disclosed for example in U.S. Pat. No. 4,349,552 or WO03078400. The disclosure of these publications, however, does not encompass the 2-adamantylurea derivatives of the present invention nor the use of the disclosed compounds as 11β-HSD1 inhibitors.
Thus, as there remains a continuing need in advantageous therapeutics, a preferred object of the present invention was to provide new pharmaceutically active compounds for the treatment of diseases such as diabetes, obesity, glaucoma, osteoporosis, cognitive disorders, immune disorders, depression, hypertension, and others.
The citation of any reference in this application is not an admission that the reference is prior art to this application.